MB-7656 Fix warning about possibly uninitialized var

Change-Id: Id4849e5f0067a6471469a5d2dfd55eecfe8d1605
Reviewed-on: http://review.couchbase.org/25602
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Reviewed-by: Fulu Li <fulu@couchbase.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>